C++ Tutorial/Development/delete
Версия от 14:21, 25 мая 2010; (обсуждение)
Содержание
Delete an array of objects
#include <iostream>
#include <cstdlib>
#include <new>
using namespace std;
class Point {
int x, y;
public:
Point() {x = y = 0;}
Point(int px, int py) {
x = px;
y = py;
}
void show() {
cout << x << " ";
cout << y << "\n";
}
void *operator new(size_t size);
void operator delete(void *p);
void *operator new[](size_t size);
void operator delete[](void *p);
};
// new overloaded relative to Point.
void *Point::operator new(size_t size)
{
void *p;
cout << "In overloaded new.\n";
p = malloc(size);
if(!p) {
bad_alloc ba;
throw ba;
}
return p;
}
// delete overloaded relative to Point.
void Point::operator delete(void *p)
{
cout << "In overloaded delete.\n";
free(p);
}
// new overloaded for Point arrays.
void *Point::operator new[](size_t size)
{
void *p;
cout << "Using overload new[].\n";
p = malloc(size);
if(!p) {
bad_alloc ba;
throw ba;
}
return p;
}
// delete overloaded for Point arrays.
void Point::operator delete[](void *p)
{
cout << "Freeing array using overloaded delete[]\n";
free(p);
}
int main()
{
Point *p1, *p2;
int i;
try {
p1 = new Point (10, 20); // allocate an object
} catch (bad_alloc xa) {
cout << "Allocation error for p1.\n";
return 1;;
}
try {
p2 = new Point [10]; // allocate an array
} catch (bad_alloc xa) {
cout << "Allocation error for p2.\n";
return 1;;
}
p1->show();
for(i=0; i<10; i++)
p2[i].show();
delete p1; // free an object
delete [] p2; // free an array
return 0;
}In overloaded new. Using overload new[]. 10 20 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 In overloaded delete. Freeing array using overloaded delete[]
delete class array and return memory to heap
#include<iostream.h>
class examp
{
int i,j;
public:
void init(int a,int b){
i=a,j=b;
}
int product() {
return i*j;
}
};
main()
{
examp *ptr;
int i;
ptr=new examp[6];
if(!ptr)
{
cout<<"Allocation error.\n";
return 1;
}
for(i=0;i<6;i++)
ptr[i].init(i,i);
for(i=0;i<6;i++)
{
cout<<"Product["<<i<<"]is:";
cout<<ptr[i].product()<<"\n";
}
delete[]ptr;
return 0;
}Product[0]is:0 Product[1]is:1 Product[2]is:4 Product[3]is:9 Product[4]is:16 Product[5]is:25
Global delete
#include <iostream>
#include <cstdlib>
#include <new>
using namespace std;
class Point {
int x, y;
public:
Point() {}
Point(int px, int py) {
x = px;
y = py;
}
void show() {
cout << x << " ";
cout << y << "\n";
}
};
// Global new
void *operator new(size_t size)
{
void *p;
p = malloc(size);
if(!p) {
bad_alloc ba;
throw ba;
}
return p;
}
// Global delete
void operator delete(void *p)
{
free(p);
}
int main()
{
Point *p1, *p2;
float *f;
try {
p1 = new Point (10, 20);
} catch (bad_alloc xa) {
cout << "Allocation error for p1.\n";
return 1;;
}
try {
p2 = new Point (-10, -20);
} catch (bad_alloc xa) {
cout << "Allocation error for p2.\n";
return 1;;
}
try {
f = new float; // uses overloaded new, too
} catch (bad_alloc xa) {
cout << "Allocation error for f.\n";
return 1;;
}
*f = 10.10F;
cout << *f << "\n";
p1->show();
p2->show();
delete p1;
delete p2;
delete f;
return 0;
}10.1 10 20 -10 -20
Memory management new-delete
#include <iostream.h>
#include <stdlib.h>
int main ()
{
char input [100];
int count,n;
long * longPointer, total = 0;
cout << "How many numbers do you want to type in? ";
cin.getline (input,100);
count=atoi (input);
longPointer= new long[count];
if (longPointer == NULL)
exit (1);
for (n=0; n<count; n++)
{
cout << "Enter number: ";
cin.getline (input,100);
longPointer[n]=atol (input);
}
cout << "You have entered: ";
for (n=0; n<count; n++)
cout << longPointer[n] << ", ";
delete[] longPointer;
return 0;
}How many numbers do you want to type in? 1 Enter number: a You have entered: 0, "
object in existence after deletion
#include<iostream.h>
class MyClass
{
static int total;
public:
MyClass()
{
total++;
}
~MyClass()
{
total--;
}
int gettotal()
{
return total;
}
};
int MyClass::total=0;
main()
{
MyClass o1,o2,o3;
cout<<o1.gettotal()<<" objects in existence\n";
MyClass *p;
p=new MyClass;
if(!p)
{
cout<<"Allocation erroe\n";
return 1;
}
cout<<o1.gettotal();
cout<<" object in existence after allocation\n";
delete p;
cout<<o1.gettotal();
cout<<" object in existence after deletion\n";
return 0;
}3 objects in existence 4 object in existence after allocation 3 object in existence after deletion
Using new and delete of array
#include <iostream.h>
class Point
{
int x;
int y;
public:
Point(){
x = 0;
y = 0;
}
Point(int a,int b=0) {
x = a;
y= b;
}
void Set (int a,int b=0) {
x = a;
y = b;
}
void Display() {
cout << "x = "<< x << " y = "<< y << endl;
}
~Point() {
cout << "Destruct obj.\n" ;
}
};
int main()
{
Point *p;int i;
const int Length = 3;
p=new Point[Length];
if(!p)
{
cout << "allocation failure\n";
return -1;
}
for (i=0;i<Length;i++)
p[i].Set(i*10,-i*10);
for (i=0;i<Length;i++)
p[i].Display();
delete []p;
return 0;
}x = 0 y = 0 x = 10 y = -10 x = 20 y = -20 Destruct obj. Destruct obj. Destruct obj.
